This invention pertains generally to mirror arrangements for directing a beam of wave-propagated energy and particularly to mirror arrangements for steering a laser beam.
It has been known for many years in the art that the direction of a beam of wave propagated energy, as for example a beam of light, may be changed by reflecting light from one or more movable mirrors. By controlling the orientation of each one of such mirrors with respect to the longitudinal axis of the beam being directed, the final direction of the beam may be changed, within relatively wide limits, as desired.
When it is desired to steer a beam wherein radiant flux density is relatively high, as for example a laser beam, conventional flat or curved mirrors may not be capable of withstanding damage from the beam being directed. To overcome such a difficulty, it is known in the art that steerable mirror arrangements may be made following the disclosure in my U.S. Pat. No. 3,790,258, assigned to the same assignee as this application. Briefly, according to my just cited patent, a steerable catoptric arrangement usable with a high powered source, such as a laser, may be provided by two sets of mirrors, the first being adapted to focus a laser beam to be steered to a point (or, alternatively, to form a collimated beam from such laser beam) aand the second set being adapted to be movable about the point (or, alternatively, to be movable with respect to the collimated beam) and to form an emergent beam whose direction may be changed as desired. While the various embodiments shown in my cited patent are useful in many applications, experience has proven that the number of reflecting surfaces required may militate against the use of any of such embodiments in some applications. For example, if a transportable system is desired to allow the beam from a high powered laser to be aimed at any point within a field surrounding a vehicle, it is extremely important, if not essential, that the beam steering arrangement have as few reflecting surfaces as possible. In other words, for obvious reasons of efficiency, weight and size, the number of mirrors making up the beam steering arrangement to direct the beam from a transportable high powered laser should be kept to a minimum.
It is highly desirable that any steerable catoptric arrangement be disposed so that the position of the "focused" beam be controllable with a high degree of precision. That is, it is highly desirable in many cases to provide means which allow the position of a steered beam to be controlled with a higher degree of precision than is possible when any conventional gearing mechanism is used to move one or more mirrors relative to a beam to be steered to effect steering.